The prophet 5 is an alltime classic let down only by its lack of polyphony and its tempermental nature, the REV-1s (182 built) are quirky to say the least but are the best looking and sounding, these (and the REV2s) have a horrible reputation for unreliability but my REV-1 is still going strong. Rev-3 (1980) introduced Curtis chips and a slightly blander sound, better reliability, Rev 3.1 added instant editing of presets, Rev 3.2 the digital interface and Rev 3.3 120 memories. Far better sounding than the later Midi equipped 600 or T8, the Prophet 10 was basically two REV-3.* models in one massive package with a dual manual keyboard and a poly sequencer, very nice Very interesting sounds can be created with the Polymod section (one of the P5s best points) usually by tweaking blindly rather than actually thinking what you`re doing. just for the record, it would seem that the REV-1/2 aren`t as unreliable as people make out and the REV-3.*s aren`t bullet proof either, also the difference in sound isn`t as great either, things in the analog world do get blown out of proportion, best bet is a REV-3.3 with a Kenton Midi kit fitted, what a synth!!..